More than one-in-three of the 317 alleged victims of sexual assault who sought help from the busiest treatment centre in the country last year had consumed the equivalent of four pints of beer.

A further 36 women and men, who could not remember if they were attacked, had taken alcohol prior to the alleged assault, according to the annual report of the Sexual Assault Treatment Centre at the Rotunda Hospital in Dublin.

The centre said that 32 people treated in 2015 had taken illegal drugs.

It is one of six sexual assault treatment units in the country where alleged victims are medically examined.

The centres - which are located in Dublin, Galway, Cork, Mullingar, Waterford and Donegal - treated 685 women and men last year, an increase of 57 compared to 2014.

Of these, nearly half had consumed the equivalent of two pints of beer in the 12 hours prior to the assault.

The reports, seen by the Irish Independent, follow widespread debate about women and men who are left vulnerable to attack after consuming too much drink or drugs.

The issue led to heated discussion between panellists on topical RTÉ show 'Cutting Edge'.

The directors of the sexual assault treatment centres have noted the levels of alcohol consumed, but pass no judgment.

The report said 631 of those treated were women and 54 were men, with an average age of 25. The youngest was 13 and the oldest was over 80 years of age. Three-quarters of the clients reported the incident to the gardaí.

Six in 10 women were seen early enough to get emergency contraception and others were given prophylaxis for chlamydia and HIV.

The Cork centre said that, of 100 clients, nearly one-in-four had drunk the equivalent of five pints of beer.

The centre also noted the majority of assaults took place between 9pm and 9am. Eight cases took place on a notable day or event, with four on New Year's Day and one on St Patrick's Day.

The centres have received funding this year to implement a secure storage of forensic evidence.

This allows them to store forensic samples for a defined period for people who are uncertain about whether they want to report an incident to the gardaí.

As forensic evidence deteriorates quickly, international best practice advocates the collection and secure storage of samples as soon as possible after an incident.

The alleged victim can then evaluate options in terms of engaging with the criminal justice system, with the chain of evidence maintained.